The recent advances in the treatment of cancer have shown that in order to plan a suitable cancer treatment and to determine a precise prognosis, it is necessary to have sensitive methods available for detecting the presence of cancer, the type of cancer and the stage thereof in order to determine its specific location and its possible spread to other tissues. A precise diagnosis of the cancer can contribute to a reduction in the number of deaths due to this disease and improve the quality of life of patients, given that it allows the most appropriate treatment to be chosen (chemotherapy, surgical removal, etc.) and helps reduce the inconveniences for the patient by defining the end point of the therapeutic treatment.
The prognostic markers provide important information for the treatment and development of cancer in patients. In fact, for the application of systemic adjuvant therapy in the treatment of some types of primary cancers, identification of patients at high and low risk is one of the main goals. Several prognostic markers are known, both classical, such as tumor size, state of lymph nodule, histopathology, state of steroid receptor, and second generation markers, such as rate of proliferation, DNA ploidy, oncogenes, growth factor receptors and some glycoprotein receptors, which are useful for taking therapeutic decisions (McGuire, W. L., Prognostic Factors for Recurrence and Survival, in “Educational Booklet American Society of Clinical Oncology,” 25th Annual Meeting, 89-92 (1989); Contesso et al., Eur. J. Clin. Oncol., 25: 403-4′9 (1989)). Although none of the known prognostic markers completely satisfy the objective of distinguishing between patients of high and low risk, the combination of different markers can improve the prediction of the prognosis of the patient, and so the search continues for new prognosis markers that can be added to the current ones to aid in the corroboration of the prognosis of the cancer, its progression and the residual disease after treatment.
On the other hand, most of the methods used for the detection of cancerous cells have a limited sensitivity, although the molecular methods based on analysis of nucleic acids have improved said sensitivity (Burchill S. A. & Selby P. J., J. Pathol. 190: 6-14 (2000)). Nevertheless, none of these strategies allows an invasive tumor cell to be distinguished from a non-invasive tumor cell.
The Slug gene is a gene present in vertebrates. It codes for a transcription factor of the “zinc fingers” type (SLUG), implicated in epithelial-mesenchymal transitions (Nieto et al., Science 264: 835-849 (1994)).